What 'dfens' has said appears to be incorrect. imapsync is under the WTFPL as per http://www.linux-france.org/prj/imapsync/COPYING - this license is listed on http://www.gnu.org/licenses/license-list.html as "... a free software license, very permissive and GPL-compatible." , and mentioned on http://www.opensource.org/minutes20090304 as "no different from dedication to the public domain". The author happens to require payment if you want a copy of the latest code FROM HIS SITE, but the terms of his license allow further redistribution (such as from rot13 uggcf://srqbenubfgrq.bet/eryrnfrq/vzncflap/ :)